- [X] general overview of what happens (basically the expected "before" and "after" states)- [X] rough ETA of how long the process takes, and if it scales out with number of hosts or anything like that (I am pretty sure it's constant-ish time but need to confirm)- [X] links to info about rewriting modules to support puppet 4- [X] document [flag day](https://en.wikipedia.org/wiki/Flag_day_(computing)) style upgrade, where Katello and all capsules are upgraded in a single outage window.- [X] document gradual cutover upgrade, where users spin up a new puppet 4 capsule, move systems over, then decommission puppet 3 capsule at a later date.- [X] docment special considerations for self-registered Katello installations- [X] confirm and document that puppet 3 and 4 can't coexist on the same katello server- [X] links to more info